Stoats in New Zealand
Encyclopedia
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
to control rabbits and hares, but are now a major threat to the native bird population. The natural range of the stoat is limited to parts of the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
. Immediately prior to human settlement, New Zealand did not have any land-based mammals apart from bats, but both Māori and European
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
settlers introducing a wide variety of animals.
Introductions of stoats
The rabbitRabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
was introduced as a food and game animal by European settlers and by the 1870s, it was becoming a serious threat to the newly developed farming economy. Farmers began demanding the introduction of mustelids (including stoats) to control the rabbit plague. Warnings about the dangers to bird life from stoats were given by scientists in New Zealand and Britain, including the New Zealand ornithologist Walter Buller
Walter Buller
Walter Lawry Buller KCMG was a New Zealand lawyer, naturalist and ornithologist.Buller was the author of A History of the Birds of New Zealand , with illustrations by John Gerrard Keulemans. In 1882 he produced the Manual of the Birds of New Zealand as a cheaper, popular alternative...
. The warnings were ignored and stoats began to be introduced from Britain in the 1880s, then, within six years, drastic declines in bird populations were noticed.
In December 2010, a stoat was seen on what was thought to be the stoat-free Kapiti Island
Kapiti Island
-External links:* , Department of Conservation* * , Nature Coast Enterprise *...
, and by August the next year DOC had managed to kill three. It is thought that they could not have swum the five kilometre stretch of open sea from the Kapiti Coast.
Threat to bird life
New Zealand has a high proportion of ground-nesting and flightless birds, due to the long geographical isolation and a lack of mammal predators. The native birds have evolved to fill the niche that is otherwise filled by mammals. Stoats are the greatest threat to these ground-nesting and hole-nesting birds since they have very little means of escaping predation. In addition to birds, stoats eat insects and mice. During times of a "beech mast", when the southern beeches (NothofagusNothofagus
Nothofagus, also known as the southern beeches, is a genus of 35 species of trees and shrubs native to the temperate oceanic to tropical Southern Hemisphere in southern South America and Australasia...
species) produce a far greater than normal amount of seed, the stoat population undergoes changes in predation behaviour. With high beech-seed numbers, rats and mice become more plentiful; this increase in prey encourages stoat breeding. The higher stoat numbers reduce the rodent population and the stoats then prey on birds. For instance, the endangered takahe
Takahe
The Takahē or South Island Takahē, Porphyrio hochstetteri is a flightless bird indigenous to New Zealand and belonging to the rail family. It was thought to be extinct after the last four known specimens were taken in 1898...
's wild population dropped by a third between 2006 and 2007, after a stoat plague triggered by the 2005–06 mast wiped out more than half the takahe in untrapped areas.
Control measures
Stoats are difficult to control since they are bait-shy, trap-wary and have a high fecundityFecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
. In some areas where there are populations of endangered birds, a programme of stoat-trapping has been implemented. The most common method of trapping is to use a stoat tunnel - a wooden box with a small entrance at one end to allow the stoat to enter. The bait is an egg and a trap is placed in the tunnel to kill the stoat. Mainland Islands, protected areas that have intensive control of introduced pests, have stoat trapping on their perimeter. Predator-proof fences are used to keep stoats out of protected areas with the use of fine wire mesh netting. Methods of restricting stoat breeding are also being investigated.
Legislation
Although stoats were recognised as a potential pest before being introduced into New Zealand, they were given protection as late as 1936. As a means of preventing a loss of biodiversityBiodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
, there are now penalties for introducing stoats into protected area
Protected area
Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...
s.
See also
- Conservation in New ZealandConservation in New ZealandConservation in New Zealand has a history associated with both Māori and Europeans. Both groups of people caused a loss of species and both amended their behaviour after realising their effect on indigenous flora and fauna.-Protected areas:...
- Birds of New ZealandBirds of New ZealandBeing an island nation with a history of long isolation and having no land mammals apart from bats, the birds of New Zealand have evolved to include a large number of unique species. Over the 65 million year isolation from any other land mass New Zealand became a land of birds and when Captain...
- Invasive species in New ZealandInvasive species in New ZealandA number of introduced species, some of which have become invasive species, have been added to New Zealand's native flora and fauna.Both deliberate and accidental introductions have been made from the time of the first human settlement with several waves of Polynesian people at some time before the...
External links
- Stoats at the Department of Conservation
- Ferret and Stoat Research at Landcare Research
- Wild about New Zealand - Stoats (educational resource)
- Stoats and cats at Te Ara - the Encyclopedia of New Zealand